A Rare Natural Benzo[<i>k,l</i>]xanthene as a Turn-Off Fluorescent Sensor for Cu²⁺Ion

• Main Authors: Giuseppe Floresta, Nunzio Cardullo, Carmela Spatafora, Antonio Rescifina, Corrado Tringali
• Format: Article
• Language: English
• Published: MDPI AG 2020-09-01
• Series: International Journal of Molecular Sciences
• Subjects: polyphenols; lignans; fluorescent sensor; natural-derived ligand
• Online Access: https://www.mdpi.com/1422-0067/21/18/6933
• ISSN: 1661-6596; 1422-0067

Rapid and efficient analyses of copper ions are crucial to providing key information for Cu²⁺ in living cells because of their biological importance. In this study, we reported one new turn-off fluorescent sensor for Cu²⁺ with a benzo[<i>k,l</i>]xanthene core, which served as an efficient cation sensor for copper ion over a wide range of other cations (Na⁺, K⁺, Ag⁺, Hg²⁺, Cd²⁺, Co²⁺, Ni²⁺, Zn²⁺, Mg²⁺, and Fe³⁺) owing to the catechol group in the aromatic core. The sensor showed selectivity for Cu²⁺ over other ions; the log<i>K</i>_β for Cu²⁺ binding to compound <b>1</b> had a value of 13.265. In the presence of Cu²⁺, sensor <b>1 </b>provided significant fluorescence decrement; Co²⁺, and Ni²⁺caused a fluorescence decrement when employed at a higher concentration than Cu²⁺, while Na⁺, K⁺, Hg²⁺, Cd²⁺, Zn²⁺, and Mg²⁺ metal ions produced only minor changes in fluorescence intensity. Fluorescence experiments demonstrate that compound <b>1</b> may have an application as a fluorescent probe for detecting Cu²⁺ with a limit of detection of 0.574 µM.